PURPOSE: Radiation Therapy Oncology Group (RTOG) 95-17, a Phase II trial to evaluate multi-catheter brachytherapy (mCathBrachy) as the sole method of radiation therapy for Stage I II breast cancer (BrCa), was the first cooperative group trial in North America to evaluate accelerated partial breast irradiation (APBI) and include patient-reported outcomes (PROs). This report presents the year-5 toxicity and cosmesis data.; METHODS AND MATERIALS: After lumpectomy and axillary dissection for invasive BrCa (tumor size <3 cm with zero to three positive lymph nodes), 100 patients (pts), 98 evaluable, were treated (txed) with mCathBrachy from 1997 to 2000 with 34 Gy administered twice daily in 10 high-dose-rate fractions or 45 Gy in 3.5-6 days as a low-dose-rate implant to 1-2 cm beyond the lumpectomy bed. The PROs and physician-reported outcomes of toxicity, cosmesis, and tx satisfaction at year-5 are reported here, defined as data submitted 54-78 months after tx.; RESULTS: Grade (G) 1-2 skin toxicity developed in 78% of the pts and G3 in 13% (no G4). The tx effects included skin dimpling/indentation (37%), fibrosis (45%), telangiectasias (45%), skin catheter marks (54%), and symptomatic fat necrosis (15%). Breast asymmetry was reported in 73%. Rates of excellent-to-good cosmesis were similar between PROs (66%) and radiation oncologists (68%). The PROs of tx satisfaction at year-5 was 75%.; CONCLUSIONS: RTOG 95-17 documents the year-5 skin toxicity and tx effects of mCathBrachy APBI, which are associated with PROs of good-to-excellent cosmesis and high tx satisfaction. This emphasizes the importance of PROs when assessing BrCa tx. National Surgical Adjuvant Breast and Bowel Project B39/RTOG 0413 will allow for definitive comparisons between APBI and whole breast radiation therapy. (C) 2014 Published by Elsevier Inc. on behalf of American Brachytherapy Society.